/*
 * Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package com.machinepublishers.glass.ui.monocle;

import java.util.Arrays;

class RunnableQueue {

    private Runnable[] queue = new Runnable[32];
    private int start;
    private int count;

    private int modulo(int index) {
        if (index >= queue.length) {
            index -= queue.length;
        }
        return index;
    }

    synchronized void postRunnable(Runnable r) {
        if (count == queue.length) {
            Runnable[] newQueue = new Runnable[(queue.length * 3) / 2];
            System.arraycopy(queue, start, newQueue, 0, queue.length - start);
            System.arraycopy(queue, 0, newQueue, queue.length - start, start);
            queue = newQueue;
            start = 0;
        }
        queue[modulo(start + count)] = r;
        count ++;
        notifyAll();
    }

    synchronized Runnable getNextRunnable() throws InterruptedException {
        while (count == 0) {
            wait();
        }
        Runnable r = queue[start];
        queue[start] = null;
        start = modulo(start + 1);
        count --;
        return r;
    }

    synchronized void clear() {
        Arrays.fill(queue, null);
        count = 0;
    }

}
